Pneumatic impact device



Patented July 22, 1952 PNEUMATIC IMPACT DEVICE Donald E. Beckettandvwilliam N. Beckett, Wilmington, Ohio, assignors of one-fourthto Heber W. Harcum and one-fourth to J. Bates Harcum, both of Wilmington, Ohio 7 Application April 5, 1949, Serial No. 85,622

This invention relates to a pneumatic hammer of the type adapted to deliver one working stroke or blow in response to each actuation of a control or trigger valve.

An object of the invention is to provide a pneumatic impact hammer which includes a reciprocable hammer piston which is driven forwardly in a power or impact stroke and then retracted rearwardly therefrom by means of fluid pressure which'is operative to normally maintain the piston at one or the other ends of its stroke pending the application of a deliberate action on the part of an op'erator'for shifting the piston to the other end' of its stroke.

A further object of the invention is to provide a universal type pneumatic impact hammer which may be operatively associated, as a piece of standard equipment, to and with various types of work engaging members, such as, by way of example, nailing guns, punch presses, stapling machines, punching mechanisms, broachers, shears, riveting guns, tamping hammers, chippingmachines, and the like.

Still a'further object of the invention is to provide a pneumatic impact device which includes a reciprocable hammer piston, the stroke of which is less than the overall length of the piston. Another object of the invention is to provide a pneumatic impact device which is so constructed and arranged that the hammer piston is accelerated throughout its driving stroke up to the mo- 5 Claims. (01. 121 21) ment 'of impact with a work engaging member associated therewith.

A further object of the invention is to provide a pneumatic impact device wherein the hammer piston isfree of bounce-back or rebound after completion of a driving stroke, said piston being maintained at the end of its power stroke under full line pressure until released therefrom by 'a deliberate act on the part of the operator.

Another object of the invention is to provide a pneumatic impact device wherein the hammer is maintained in a fully retracted position by air pressure confined within a comparatively small air chamber as compared with the cross-sectional area of the cylinder behind the hammer, thereby eliminating, for all practical purposes, back pressure which "would retard the forward driving stroke of the hammer.

Another object of the invention is to provide a' simple, yet highly effective means for controlling an operating valve means for controlling the operating characteristics of the hammer piston of a pneumatic impact device, wherein the operating characteristics of the valve are pneumatically controlled, said valve being so constructed and arranged as to normally direct full line pressure to the hammer piston for driving and maintaining itat one or the other ends of its stroke.

-' Still another object of the invention is to provide a pneumatic impact device which comprises an integral unit capable of being operatively associated'with any desired type of cradle, housing or handle thereby greatly enhancing its overall utility.

Another object of the invention is to provide a pneumatic impact device having the hereinabove described characteristics which is considerably more efficient. less expensive and simpler in construction than any other pneumatic impact device. of which we are aware. By way of example, when operated on pounds air pressure thru a 10 inch stroke in a cylinder having an inside diameter of 3 inches, our hammer will develop and deliver a 50,000 pound blow to a suitable work engaging member associated therewith. I

These and other objects are attained by the means described herein and as disclosed in the accompanying drawings, in which:

Fig. 1 is a sectional view taken thru a pneumatic impact tool embodying the teachings of the present invention, showing the relationship of variousparts thereof at the start of apower stroke.

Fig. 2 is a view similar to Fig. 1 but showing the relationship of the various elements at the start of areturn stroke of the hammer piston.

With reference now to Figs. 1 and 2,the numeral l0 indicates a cylinder within which a hammer piston I2 is reciprocably mounted. The diameter of the body portion of piston I2 is of a dimension less than the inside dimension of cylinder ID for providing anair chamber [4 therebetween. The difference in diameters may, by way of example, approximate. from A1 to /2 inch.

If desired, the rear portion of piston [2 may be enlarged as at I6, said enlarged portion dimensioned for a loose sliding fit within the cylinder. Suitable sealing means, such as, by way of example, an O-ring l8, or the like, may be secured to and carried by the rear portion of piston 12, said sealingmeans being receivable within annular groove 20 whereby to engage the inner face of cylinder l0 for providing a sliding air and fluid tight fit. I

At this point,- it should be clearly understood that the overall stroke of piston I2 is of a dimension less than its overall length.

In the preferred embodiment of the invention the forward end 22 of the hammer piston is adapted to engage rear face 24 of an anvil 26 of a work engaging member suitably secured to the forward end of the cylinder. In Fig. 1, the work engaging member includes an outer casing 28 which is secured in abutting relationship to annular sleeve 30 carried by'the forward end of cylinder ID by means of a strap-like member 32.

Cylinder I0 and casing 28 of the work efngag ing member may be received within a combinationhand grip and supporting unit denoted generally by the numeral 40, it being understood gun, a punching mechanism, a breaching device,

a shearing mechanism, a stapling machine, or

z w Y "[fbe freelyexhausted incident to forward motion of piston a other suitable member. 7

Sealing means 42 are secured relative to the .0

forward end of cylinder ill for engagingthefor ward portion of the hammer piston when in a" be interconnected by'means of a conduit 94 to annular port 821 of the valve: Annular ports 55 and '64 are exhaust ports suitably vented through valve block 52 to the atmosphere. With refer ence again to Fig. 1, it will be noted that port 92 is .in open communication with exhaust port fully retracted position, thereby :defining the front wall or end of an air chamber I d, the rear wall or end of which is defined by sealing means [8. If desired, an annular sleeve is secured to th'e'forward end of cylinder I!) having an undercutportion 44, carrying sealing means 42. [The internal diameter of sleeve 30 is dimensioned for a sliding fit with the body portion of piston I2,

vsaid sleeve providing a bearing or alignment support for the piston incident to its reciprocation withinthe cylinder.

' With reference now to-i Fig. 2, itLwill be observedthatthe area of air chamber M is quite small during those periods of time when piston ,.1

I2 is disposed at the forward end of its power or driving'stroke, said area varying fromaxmaximum when the piston is fully retracted, as in Fig.

1, to a minimum when the piston is fully extended as in Fig, 2.

Theoperating characteristics of the hammer piston are controlled by a value assembly denoted'generally by the numeral which may be received and housed Within that end of cylinder H] remote fromthe Work engaging'member. s.

"We-have tainedwhenp'ne'umatic'means are used for effecting reciprocation of piston rod for con- 6-! whereby the air within air chamber M will ound that excellent resultsiare obtrollingthe actuating characteristics of hammer piston It. An auxiliary air chamber I00 may be provided rearwardly of valve block 52 whereby" to house therear end of piston rod 66. 2 Air from-passageway =89 may be introduced into auxiliary chamber H30 thru conduits 1G2 and HM, the flow of air being controlled by -means of valve head; (05 secured toand carried by valve'stem lllB'reciprocably mounted inblock H3 suitably threaded or sealed in element-4B as at H l. The valve stem is normally urged to the right to a seated position by means, of spring 1 l0. Valve head 195 is-adapted to seat'against a suitable valve :seat' H2: (see Fig. 2), for preeluding a flow of air from passageway to conlC'he body of "valve stem I08 is-provided with an undercut portion H4 thru which the air within the auxiliarychamber I00 and conduits Hi2 and I34 may beexhausted when the valve stem is seated. When the pressure within the auxiliary chamber: lfifi has thus :been;,re-

' leased piston rod 66 will ebe, shifted rearwardly 56, 58, B0,t2 and 64 are provided in-open com- 7 munication with axial bore 54. A piston 'rod 68 is reciprocably mounted in said bore, said piston rod'including pistons 68, 10, Hand 14, which are constructed and arranged to'cooperate with variousof said annular ports for con'trollin'gthe flow ofairtothe hammer piston. V e "l vWith reference now to Fig; ,1, piston rod: 5 6 i's disposed in the forward ofits two normal posi- .ti0ns,iwherein pistons 19 and i2 are located on opposed sides of adjacent ports 58 and fifl'thereby interconnecting said ports. Port 68 is disposed in opencommunication with passageway 86 which extends thru valve. block 52; the wall of cylinder 1? piston #2 will be driven forwardly or rearwardly l8, thence into element, 40. 'Passageway BQ'is in open communication with passagewayj82 the lower free end of which is normally connected toa source of air under pressure.

From the foregoing, it will be observed that full line pressure will always be maintained erance to Fig. 2, it'will be observed that inlet port 92 is so located as to' be in open communication withthe minimumarea of air chamber I l as. defined by piston {2 when at theforward end of a, power stroke. Inlet port 92 may iii from the position illustrated in Fig. 1- to the-pos'ition illustrated in Fig. 2 by means of the'tprcssure within cylinder it which pressure willact upon forward end l is of piston. 68, thereby connecting'th'e line pressuregtoannular port 62' and inlet port 92 while: interconnecting passageway '99 to exhaust portBt. Y

" Actuation of valve stem I H38. may be effected by means of a lever l2!) pivotally secured'as at EZZ-to handle portion 124 of element 40; It will-be understood that lever I20 will be moved forwardlyfor unseating valve stem IDS-incident to a squeezing faction applied to hand grip I24 by the operator.

-Tl1e;extent of. axial travel of piston rod 66 .may be governed by collar I34 threadablysecured to the rear end of the piston rod, said collar including portions adapted to abut against therear face of valve block 52 for limiting-the forward travel of the piston rod. I 7

From the foregoing, it will be observed that a the rear face of the hammer piston 12 for driving the piston forwardly with ever increasing acceleration up to the time ofits impact with anvil 26 of a work engaging member. The effectiveness of our. device will immediately become apparent when, it is noted that We are able to develop a 50,000 pound impact thru a 10 inch stroke in a 3% inch cylinder at pounds air pressure. A device having a cylinder with a 1 inch inside diameter and an effective'piston stroke of 4 inches operating on '75 pounds pressure will operate a commercial nailinggunwith such effectiveness as to drive and countersink 1% inch rectangular nails into hard Wood.

It will be observed that'air is utilized to control both the actuatingvalue and the hammer piston whereby the need of springs has been completely eliminated. The structural characteristics of the device are such that there is substantially no back'pressureopposing the forward driving stroke of piston [2. This is true because of the small area of air chamber M, the total or overall area of which is continuously reduced as piston [2 moves forwardly.'*Although the cross-sectional areaof air chamber I4 is small, it is nevertheless quite suflicient to effect an almost instantaneous return of piston l2 from the fully extended position of Fig. 2 to the fully retracted position of Fig. 1. Experiments and actual usage have conclusively proven that the operating cycle is practically instantaneous with actuation of lever J29.

If desired,- 'a spring, not illustrated, may be interposed between collar I34 and the end of valve block 52 for precluding accidental or u intentional shifting of piston rod' 66 to an impact delivering-position of Fig. 1 during those periods of time when the line pressure has been disconnected or during those periods of time when the pressure on opposite ends of the piston rod is substantially equal so that it could shift of its own weight incident to movement of the device, such as, in the normal handling and usage thereof. a

What is claimed is: I 1. A manually portable pneumatic toolof the character described comprising a cylinder, a-

hammer piston reciprocable therein, a work engaging member at one end of said cylinder disposed to be struck by said piston, a valve assembly secured to, carried by andhousedfwithin the other end of said cylinder, an air; chamber pro-' vided between said piston and cylinder, sealing means secured to and carried by the rearportion of said piston engaging the inner wall ofsaid cylinder, sealing means secured relative to said cylinder engaging the forward portion of said piston when in a fully retracted positioman air port in open communication with the air chamber surrounding said piston, said valve assembly including a valve block in that end of the cylinder remote from said work engaging member, said block having an axial bore having aplurality of annular ports in-open communication therewith,

a piston rod reciprocably mounted in said bore, pistons on said rod for cooperation with various of'said ports, means for continuously directing compressed air to one of said annular ports, means interconnecting a second annular port in open-communication with said air port, means interconnecting a third annular port in open communication with said cylinder rearwardly of the piston when in a fully retracted position, said piston rod reciprocable for connecting one or the other of said second and'third annular ports in open communication with said first annular cable therein, a work engaging member'at one end of said cylinder disposed to be struck by said piston, a valve assembly secured to, carried by and-housed within the other end ofsaidcyl- ,inder, an air chamber provided between'said piston and'cylinder, sealing means secured to and carried by the rear portion of said piston engaging the inner wall" of saidcylinder, sealing means secured relative to said cylinder engaging the forward portion of said piston when in a fully retracted position, an airport inopengcommunication with the air chamber surrounding said piston, said valve assembly including a valve piston, rod reciprocably mounted in saidbore, pistons on said rod for cooperation with various of said ports, means for continuously directing compressed air to one ofsaid annular ports,

' means interconnecting-a second annular port open communication withsaid air port, means interconnecting a .third annular port in open communication with said'cylinder rearwardly of the-piston when in a fully retracted position, said piston rod reciprocable for connecting one or the other of said second and third annular, ports in open communication with said first annular port and for exhausting the other port fordriving and maintaining said hammer piston at one or the other ends of its stroke, and means operable for reciprocating said piston rodforpohtrolling the stroke of said hammer piston one end of the axial boreof said valve in open communication with-the interior of said cylinder,

, an auxiliary air chamber in open communicaretracted position.

tion with the opposite end of said axial bore, manually controlled means for selectively. direct- .ing compressed air into said auxiliary, air chamber for driving said valve piston rod forwardly for connecting saidfirst and. third annular ports for directing compressed air ontolthe rear face of said piston to drive said piston forwardlyon its power stroke, said piston rod shiftable rearwardly upon release of pressure in said auxiliary chamber for connecting said first and second annular ports fordirecting compressed air into the air chamber surrounding said hammer piston to return and maintain said piston in a fully 3. A pneumatic impact hammer comprising a cylinder, a hammer piston reciprocable therein through a power stroke and a return stroke, an air chamber surrounding said piston, sealing means secured relative to the rear portion of the piston slidably engaging said cylinder, other sealing means secured relative to the cylinder" slidably engaging said piston, said sealing means defin ng the front and rear ends of the air chamber surrounding said piston, a valve" assembly housed within the cylinder rearwardly of'the 'rearmost end of the piston when at the end of a return stroke, said assembly including a re- --ciprocable valve member in axialalignment with the cylinder and with its forward end in open communication with the interior of the cylinder, manually controlled means for selectively supplying motive fluid under full line'pressure to the rear end of said valve member for shifting it forwardlyto a position Where motive fluid will be directed into said cylinder for driving the .piston forwardly and maintainingit in arfully and of maintaining it in retracted position until the actuation of said manually controlled means.

A. A manually operable pneumatic tool of the character described comprising a cylinder, a hammer piston reciprocable therein, a work engaging member at one end of said cylinder disposed to be struck by said piston, a valve assembly secured to, carried by and housed within the other end of said cylinder, an air chamber provided between said piston and cylinder, sealing means secured to and carried by the rear portion of said piston engaging the inner wall 'ofsaid cylinder, sealing means secured relative to said cylinder engaging the forward portion of said piston when in a fully retracted position, an air port in open communicationwith the air chambersurrounding said piston, said valve as-: sembly including avalve block'disposed within that end of the cylinder remote from said work "engaging member, said block having therethrough an axial bore having-a plurality of an-- nular ports in open communication therewith, a piston rod reciprocably mounted in said bore, pistons on said rod for cooperation with various of said ports, means for continuously directing compressed air to one of said annular ports,

means interconnecting a second annular port in open communication with said air port, means interconnecting a third annular port in open communication with said cylinder rearwardly of the piston when in a fully retracted position, said piston rod reciprocable for connecting one or the other of said second and third annular ports in open communication with said first annular port and for exhausting the other port for driving and maintaining said hammer piston atone or the other ends of its stroke, one end of said piston rod normally in open communication with theinterior ofsaid cylinder rearwardly of the hammer piston, a second valve block disposed within the chamber and abutting the first valve means adapted to exhaust air from said auxiliary chamber ,for driving said piston rod to a fully retracted position by the pressure existing in said cylinder behind the hammer piston for simultaneously exhausting the air in said cylinder andinstantaneously introducing air under full pressure into said air port surrounding said hammer piston for returning it to a fully retracted position.

,5. A manually portable, pneumatic tool'of 'th character described, comprising a cylinder, a hammer piston reciprocable therein, a valve assembly secured to, carried by and housed within one'end of said cylinder, sealing means secured to and carried by the rear portion of said piston engaging'the inner walls of said cylinder forwardly of said valve assembly, sealing means sesaid pis'tonand cylinder and sealing means, said valve assembly including a valve block secured to and received within said cylinder, said valve block-having therethrough an axial bore having a plurality of laterally spaced annular ports in open communication therewith, a piston rod reciprocably mounted insaid bore, with its forward end in open communication with a second chamber defined by the interior of the cylinder rearwardly of the hammer piston, pistons on said rod for co-operationwith various of said annularports, a third chamber provided in axial alignment and in open communication with the rear end of said bore, the rear end of said piston rod in open communication with the interior of said third chamber, means interconnectingone annular port in open communication with the interior of said first chamber, means interconnecting a second annular port in open communication with said second chamber, said piston rod'reciprocable between fully advanced and fully retracted positions for connecting one or the other of said first and second annular ports in open communication with a third annular port while exhausting the other port, means for supplying motive fluid under full line pressure continuously to the third of said annular ports, means for supplying motive fluid under full line pressure to said third chamber, manually operable valve means for controlling the flow of motive fluid to said third chamber orior connecting said third chamber to exhaust, said piston rod shiftable forwardly incident to and solely by the introduction of motive fluid into saidthird chamber for thereby connecting said secondand third annular ports thereby introducing motivefluid under full line pressuredirectly into the second chamber for driving and maintaining the hammer piston forwardly of said cylinder to the forward end of its stroke,

said piston rod and hammer. piston remaining at the forward ends of their respective strokes incident to the application of motive fluid under full line pressure within the second and third chambers, said piston rod being automatically ,shiftable by the pressure within the second cham- REFERENCES orrsp The following referencesare of record in the file of this patent:

UNITED STATES PATENTS 5 Number Name Date 803,562 Dean Nov. 7, 1905 910,775 Bergh Jan. 26, 1909 932,992 Maxwell Aug. 31, 1909 942,756 King et al. Dec. 7, 1909 1,267,698 Roberts May 28, 1918 I 1,571,044 DaCosta Jan. 26, 1926 1,602,901 Hansen Oct. 12, 1926 1,656,730 Hanna Jan. 17, 1928 1,839,581 Nell Jan. 5, 1932 

